Exercise machine, physical strength evaluation method, and pulse rate meter

ABSTRACT

In an exercise machine, when a measurement starts, an electrocardiographic signal is detected by an electrocardiographic sensor 1 (ST33), a load drive is started (ST4), and heartbeat rate intervals of the electrocardiographic signal are sequentially obtained. A fluctuation of heartbeat rate intervals PI(n)% is obtained from a calculation formula in which the RR interval RR(n+1) of the current heartbeat is subtracted from the RR interval RR(n) of the previous heartbeat, which is then divided by RR(n) and multiplied by 100% (ST5). Entropy is calculated from 128 pieces of such PI (ST6). From the change of the entropy under the gradually increasing load (ST8), a minimum point of the entropy is obtained, which point is designated as an anaerobic threshold point (ST7). The load of the exercise machine is controlled employing this anaerobic threshold.

TECHNICAL FIELD

The present invention relates to an exercise machine, such as bicycleergometer, treadmill and rowing ergometer, a physical strengthevaluation method and a pulse rate meter.

BACKGROUND ART

Method and apparatus for determining exertion levels interested in thisinvention are disclosed, for example, in International Publication No.WO96/20640. According to the disclosure, heartbeat of a person engagedin training is monitored. From an electrocardiographic signal obtained,a QRS complex waveform, for example, is measured to calculate theheartbeat rate. Based on a power of a spectrum derived from theheartbeat rate, an exertion level of the exercising person isdetermined.

Further, conventional method and apparatus for measuring muscularendurance of a person engaged in exercise are disclosed, for example, inJapanese Patent Publication No. 7-38885. According to the disclosure, aload of an exercising person is calculated from the product of aheartbeat rate and a blood pressure under vasoconstriction, and from theresult, the muscular endurance is calculated.

The load of a person engaged in training or exercise has conventionallybeen measured as described above. Such measurement has also made itpossible to estimate the load of an exercising person.

Conventionally, exercise machines such as a bicycle ergometer and othershave been commercially available for health maintenance and enhancement.In some of such exercise machines, a person inputs his/her age, sex andthe like, and an exercise program is arranged according to suchinformation based on statistically predetermined exertion intensity. Forevaluation of a physical strength level, some machines have adapted amethod of estimating the maximum oxygen intake based on a change ofpulsation or the like corresponding to a change of exertion load.

There is a factor for decision of safe and effective exercise; i.e., ananaerobic threshold (hereinafter, also referred to as “AT”). Thisthreshold value of exertion intensity shows a maximum exertion level atwhich exercise can be done without an abrupt increase of lactic acid inthe blood. The AT is conventionally determined employing an invasivemethod by taking a blood sample to examine the lactic acid level, or ina restraining manner by measuring changes of oxygen and carbondioxidepartial pressures in exhalation by breathing gas analysis.

Further, for evaluation of physical strength, there are conventionallyknown methods of estimating maximum oxygen intake, maximum exertionintensity, maximum heartbeat rate and others based on a change ofpulsation or the like with respect to the exertion load.

Such conventional exercise machines and apparatuses for determiningexertion levels, however, have posed the following problems:

{circle around (1)} The data obtained from the apparatus and method fordetermining the exertion level has been used only physiologically todetermine the exertion level in training or exercise; the data has notbeen utilized effectively.

{circle around (2)} Setting of exertion intensity does not conform toworking capacity of each person; a sought-after effect cannot beobtained sufficiently from the exercise.

{circle around (3)} Although the AT is considered most appropriate asthe exertion intensity in conformity with the working capacity of theindividual, measurement of the AT is restraining and requires a specialapparatus such as a breathing gas analyzer; such a measuring apparatuscannot practically be mounted on an exercise machine.

{circle around (4)} The AT, which represents aerobic working capacityimportant for decision of physical strength, cannot be determined by ordisplayed on the exercise machine due to the reason stated in {circlearound (3)} above.

The present invention is directed to solve the above-described problems,and its object is to provide an exercise machine which allows anexertion level to be readily and accurately found so that the value canbe used for effective training.

Another object of the present invention is to provide an exercisemachine which allows an anaerobic threshold to be readily and accuratelyfound so that the value can be used for effective training.

Yet another object of the present invention is to provide an exercisemachine and a physical strength evaluating method which allow physicalstrength and exertion levels to be readily found at the same time, allowa user to understand his/her own working capacity in more detail to doappropriate exercise, and allow the physical strength and exertionlevels to be evaluated with high precision in a time period as short aspossible.

A still further object of the present invention is to provide a pulserate meter which allows an exertion level to be readily and accuratelyfound.

DISCLOSURE OF THE INVENTION

The exercise machine according to the present invention includes: a loaddevice capable of changing a load; a physiological signal measuring unitmeasuring a physiological signal noninvasively over time; an exertionlevel estimating unit estimating an exertion level based on thephysiological signal corresponding to the change of the load of the loaddevice; and a unit for controlling the load of the load device employingthe exertion level estimated.

The exertion level is estimated based on the physiological signalcorresponding to the change of the load of the load device, and the loadof the load device is controlled to come close to the estimated exertionlevel. Therefore, an exercise machine allowing a user to do appropriateexercise corresponding to his/her own working capacity can be provided.

Preferably, the exertion level estimating unit estimates the exertionlevel based on a change of the physiological signal in response to thechange of the load of the load device.

More preferably, the exertion level estimating unit estimates ananaerobic threshold as the exertion level.

The exertion level estimating unit estimates the anaerobic threshold asthe exertion level, and the load of the exercise machine is controlledbased on this threshold value. Thus, an exercise machine allowing a userto do appropriate exercise more efficiently corresponding to his/her ownworking capacity can be provided.

According to an aspect of the present invention, the exertion levelestimating unit includes a unit for calculating a fluctuation ofheartbeat power rate intervals in each electrocardiographic signaldetected, a unit for calculating a power of the fluctuation of heartbeatrate intervals and a unit for finding a convergence point of a change ofthe power with respect to the increase of the load, and estimates anexertion load corresponding to the convergence point as the exertionlevel.

The fluctuation of heartbeat rate intervals in the electrocardiographicsignal is calculated and the convergence point of the power change ofthe fluctuation with respect to the load increase is obtained toestimate the exertion level. Thus, an exercise machine capable ofevaluating the exertion level with high precision in a short time periodcan be provided.

According to another aspect of the present invention, the exercisemachine includes: a load device gradually increasing a load over time;an electrocardiographic sensor detecting an electrocardiographic signal;a unit for measuring a heartbeat rate of the electrocardiographic signaldetected while the load is gradually increased; a unit for calculating afluctuation of heartbeat rate intervals in the electrocardiographicsignal; an exertion level estimating unit estimating an exertion levelbased on the heartbeat rate and the fluctuation of heartbeat rateintervals; a unit for estimating physical strength based on a slope ofthe change of the heartbeat rate with respect to the change of the loadaround the exertion level estimated by the exertion level estimatingunit; and a unit for controlling the load device to make the load comeclose to the level corresponding to the estimated physical strength.

The heartbeat rate of the electrocardiographic signal detected whilegradually increasing the load is measured, a fluctuation of which iscalculated, and the exertion level is estimated based on the heartbeatrate and the fluctuation of heartbeat rate intervals. The load of theload device is controlled to come around the estimated exertion level.Therefore, an exercise machine allowing a user to understand his/her ownworking capacity more precisely and hence to do appropriate exercise canbe provided.

According to a still further aspect of the present invention, thephysical strength evaluating method includes the steps of: graduallyincreasing a load of a load device; detecting by an electrocardiographicsensor an electrocardiographic signal under an increasing exertion loadwhile the load is gradually increased; finding a heartbeat rate and afluctuation of heartbeat rate intervals from the electrocardiographicsignal detected; and estimating physical strength and an exertion levelat the same time from the heartbeat rate and the fluctuation ofheartbeat rate intervals thus obtained.

The electrocardiographic sensor detects the electrocardiographic signalcorresponding to the increasing exertion load, and the heartbeat rateand the fluctuation of heartbeat rate intervals are obtained from thedetected electrocardiographic signal. Based on thus obtained heartbeatrate and fluctuation of heartbeat rate intervals, the physical strengthand the exertion level are estimated at the same time. Thus, a physicalstrength evaluating method capable of evaluating the physical strengthand the exertion level with high precision in a short time period can beprovided.

According to yet another aspect of the present invention, the pulse ratemeter includes: a pulse rate sensor detecting a pulse rate signalproduced by a heart; an alarm unit demanding a gradual increase of apitch of exercise; an exertion level estimating unit estimating anexertion level based on the pulse rate signal detected by the pulse ratesensor while exercise is gradually intensified; and a unit for setting apace based on the pitch of exercise corresponding to the exertion levelestimated.

As the pulse rate meter can estimate the exertion level from the pulserate signal detected while the pitch of exercise is gradually increased,it is possible to readily find an exertion level of an individual whilehe/she is engaged in exercise in the field.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a circuit configuration of a bicycleergometer according to an embodiment of the present invention.

FIG. 2 is a perspective view of the bicycle ergometer.

FIG. 3 illustrates distribution of anaerobic thresholds with respect torespective maximum heartbeat rates.

FIG. 4 is a flow chart illustrating a processing operation for ATestimation of the bicycle ergometer of a first example.

FIGS. 5A and 5B illustrate a gradual load increase by an exercisemachine and an entropy change of fluctuation of heartbeat rateintervals.

FIG. 6 is a flow chart illustrating an example of an exercise programcorresponding to AT.

FIG. 7 is a flow chart illustrating a processing operation of thebicycle ergometer of a second example.

FIG. 8 shows a relation between the heartbeat rate and the entropy offluctuation of heartbeat rate intervals while a load is graduallyincreased in the bicycle ergometer of the second example.

FIG. 9 shows a relation between the load and the heartbeat rate whilethe load is gadually increased in the bicycle ergometer of the secondexample.

FIG. 10 shows, in a worn state, one of the electrocardiographic sensorsbeing used in the bicycle ergometers of the first and second examples.

FIG. 11 shows another electrocardiographic sensor being used in thebicycle ergometer of the first example.

FIG. 12 shows yet another electrocardiographic sensor being used in thebicycle ergometers of the first and second examples.

FIG. 13 shows, in a worn state, a pulse rate sensor being used in thebicycle ergometer according to the first embodiment.

FIGS. 14A and 14B each show, in a worn state, a blood pressure gauge forfinger being used in the bicycle ergometer according to the firstembodiment.

FIGS. 15A and 15B illustrate a way of detecting the breathing rateemployed in the bicycle ergometer according to the first embodiment.

FIG. 16 is a perspective view of a treadmill as another example of theexercise machine implementing the present invention.

FIG. 17 shows a rowing ergometer as a further example of the exercisemachine implementing the present invention.

FIG. 18 is a flow chart showing contents of processing according to asecond embodiment, for controlling a load by calculating a power offluctuation of heartbeat rate intervals.

FIGS. 19A and 19B show a relation between the load and the power offluctuation.

FIG. 20 is a block diagram showing a configuration of a pulse rate meteraccording to a fourth embodiment.

FIG. 21 illustrates how a heartbeat rate meter according to the fourthembodiment is worn by a test subject.

FIG. 22 is a flow chart showing a processing operation of the heartbeatrate meter according to the fourth embodiment.

BEST MODES FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described withreference to the drawings.

(1) First Embodiment

FIG. 1 is a block diagram showing a circuit configuration of a bicycleergometer that is an example of the exercise machine according to thefirst embodiment of the present invention. This ergometer includes: anelectrocardiographic sensor 1 detecting an electrocardiographic signal;a preamplifier 2 amplifying the output signal; a filter 3 removingnoise; an amplifier 4 further amplifying the electrocardiographic signalto an appropriate level; an A/D converter 5; a CPU 6 performing variouskinds of processing; a key input device 7; a display 8; and a loaddevice (applying a rotation load) 9.

FIG. 2 is a perspective view of the bicycle ergometer according to thisembodiment. Referring to FIG. 2, the bicycle ergometer includes: asaddle 11; a handle 12; a manipulation unit 13; pedals 14; a front footframe 15; and a hind foot frame 16. Manipulation unit 13 includes keyinput device 7 and display 8 (See FIG. 1). With this ergometer, a testsubject (an exercising person) sits on saddle 11 and works pedals 14 torotate them for exercise. Load device 9 applies a load to pedals 14 togive them weight corresponding to a degree of exertion intensity. Forthe greater load, the larger amount of exercise is naturally needed torotate pedals 14 a fixed number of times. Electrodes ofelectrocardiographic sensor 1 are attached to the chest of the subjectby means of a belt. The electrocardiographic signal detected istransmitted by radio to manipulation unit 13 and other circuits forprocessing.

FIG. 10 illustrates an example of how electrocardiographic sensor 1 isworn. A chest belt 41 incorporating a pair of electrodes and atransmitter is worn around the chest of the subject M. Handle 12incorporates a receiver (corresponding to manipulation unit 13 of FIG.2) 42.

FIG. 11 shows another example of the electrocardiographic sensor for usewith the bicycle ergometer. Electrodes 43, 44 for electrocardiographicdetection are provided in handle 12. Gripping the handles, and hence,electrodes 43, 44 with respective hands enables the electrocardiographicdetection. Electrodes 43, 44 are connected to the circuitry within thebody of ergometer.

FIG. 12 illustrates still another example of the electrocardiographicsensor used with the bicycle ergometer. Referring to FIG. 12, threeelectrodes 45, 46, 47 of G (ground), +(plus) and −(minus), respectively,are attached to the chest of the exercising person M. This sensor is ofa chest leads type with the electrodes being connected to the circuitrywithin the ergometer body by wire 48 for detection of theelectrocardiographic signal.

FIG. 13 shows an example of a pulsation sensor for use with the bicycleergometer. The pulsation sensor 49 is attached to an earlobe of thesubject M for detection of pulsation.

In a conventional exercise machine such as an ergometer, an exerciseprogram for weight reduction or enhancement of physical strength wasdetermined based on the statistic data stating that the AT point as anexample of exertion level should be around 55% of the maximum heartbeatrate (maximum exertion intensity) determined by age or the like havingbeen input.

In practice, however, the actual measurement of AT represented in % as aratio to the maximum heartbeat rate greatly differs from person toperson, as shown in FIG. 3. FIG. 3 shows distribution of the ATmeasurements of 24 male students, with their respective maximumheartbeat rates being 100%. Thus, the exercise program based on theexertion intensity statistically determined in the conventional manneris not necessarily best suited for each person.

In the bicycle ergometer according to the present embodiment, inaddition to the conventionally displayed physical strength level that isshown by estimating the maximum exertion intensity such as the maximumoxygen intake (maximum heartbeat rate), an AT as an example of exertionlevel is estimated at the same time from a fluctuation of heartbeat rateintervals, and is output for display as aerobic working capacity.

Now, the processing operation of the bicycle ergometer according to thepresent embodiment will be described with reference to the flow chartshown in FIG. 4. When measurement start key depress information is inputfrom key input device 7 to CPU 6, the measurement is started. First, anelectrocardiographic signal at rest is detected by electrocardiographicsensor 1 (step ST1; hereinafter “step” is not repeated). A calibrationoperation is performed so that this signal from electrocardiographicsensor 1 reaches a certain fixed level (ST2). To accomplish thiscalibration operation, a gain is adjusted at amplifier 4 according to asignal from CPU 6.

“Start measurement” is displayed on display 8 (ST3), and load control ofload device 9 is started (ST4). As the load of load device 9, a rampload of 15 W [watt] per minute is applied. The peak value of theelectrocardiographic signal is detected to obtain RR interval data (onecycle of heartbeat). Using thus obtained RR data, PI (Percent Index) iscalculated (ST5). Herein, the PI represents, in percentage, a ratio of adifference between the previous cycle and the current cycle to theprevious cycle, which is calculated from the following expression:

PI(n)%={RR(n)−RR(N+1)}/RR(n)×100%

Herein, this PI is called a fluctuation of heartbeat rate intervals.

From 128 pieces of this PI data, or at an interval of every two minutes,frequency distribution in percentage is calculated. From P(i)=f(i) / f,and according to the following expression (1), entropy H of thefluctuation of heartbeat rate intervals is calculated (ST6).$\begin{matrix}{H = {- {\sum\limits_{i}\quad {{P(i)}\quad \log_{2}\quad {P(i)}}}}} & (1)\end{matrix}$

Thereafter, a decision is made whether the AT point is reached (ST7). Asshown in FIGS. 5A and 5B, if the entropy decreases as the amount ofexercise increases, the decision is NO. The load is thus increasedgradually (ST8), while the PI value and entropy are calculatedcontinuously (ST5, ST6). As shown in FIG. 5A, when the entropy reachesits polarization point (minimum point), the point is regarded as the ATpoint. Thus, the decision in ST7 is YES, and this result is displayed ondisplay 8 (ST9). The result includes heartbeat rate (bPM), loadintensity (W), time (min) or the like at the AT point. After the displayof the result, the load is decreased for cooling down (ST10). After oneminute of the cooling down, application of the load is stopped, and thecontrol is terminated (ST11).

The bicycle ergometer according to the present embodiment has acapability to readily obtain the AT. Conventionally, the exertionintensity of the exercise program for weight reduction, enhancement ofphysical strength or the like was set as its ratio to the maximumheartbeat rate in percentage, e.g., 65% for weight reduction, and 75%for physical strength enhancement. Conversely, with the presentembodiment, such exertion intensity can be set like 18% less or 18%greater than the AT point. Thus, it becomes possible to adjust theexertion intensity to conform to the exertion level of the individual.

FIG. 6 is a flow chart showing an example of the process to determineexertion intensity from an estimated AT in the exercise machineaccording to the present embodiment. When the AT point is estimated(ST21), or, if the AT value of the specific person is already known andit is input via key input device 7 (ST22), then a determination is madewhether a weight reduction program is designated (ST23). If YES, theload is set to 82% of the AT (ST24). If the weight reduction program isnot designated, a determination is further made whether a physicalstrength enhancement program is designated (ST25). If YES, the load isset to 118% of the AT (ST26). If NO in ST25, control goes to stillanother process.

The bicycle ergometer according to the present embodiment is able toreadily estimate both the maximum heartbeat rate (exertion intensity)and the AT. Thus, by showing in percentage a ratio of AT to the maximumheartbeat rate (exertion intensity) for each person, it is possible toshow aerobic working capacity of the person in relation to a statisticalaverage level. Thus, with this exercise machine having such a displayoutput capability, not only the simple physical strength level, but alsothe aerobic working capacity can be output for display, so that a usercan readily know his/her aerobic working capacity that has never beenknown with ease.

Another example of the ergometer according to the present embodimentwill be described. The bicycle ergometer of this example has a circuitconfiguration similar to the one shown in FIG. 1, and again, in additionto the conventional display of physical strength level provided based onthe estimation of the maximum exertion intensity such as the maximumoxygen intake (maximum heartbeat rate), it can estimate, at the sametime, the AT from the fluctuation of heartbeat rate intervals, andoutput it for display as the aerobic working capacity.

The entire operation of the exercise machine of this example will bedescribed with reference to the flow chart shown in FIG. 7. When theoperation starts, personal data, such as age, sex or the like, isentered via key input device 7 (ST31). Next, a determination is madewhether only the AT is to be estimated (ST32). If so with only theestimation of AT having been designated via key input device 7, entropyof a heartbeat rate fluctuation at rest is calculated (ST33). If thisentropy level is less than 2.0, it is determined that the AT estimationis impossible, and the estimation is terminated (ST35). This is becausesome test subjects exhibit almost no heartbeat rate fluctuation andhence a low entropy level at rest, and therefore, even if they aresubjected to an exertion load test, the AT determination is expected tobe very difficult. Thus, it is determined in advance that the ATestimation is impossible for them, such that they need not dounnecessary exercise.

For a test subject with the entropy level at least 2, or for a subjectrequesting estimation of both the AT and the physical strength, theheartbeat rate at rest is measured (ST36) and the exertion load test isconducted. At this time, an initial load value and an exertion loadpattern of, e.g., gradually increasing ramp load are determined based onthe personal data (ST37, ST38). Specifically, as it is inefficient touse the same pattern for persons with different physical strengthlevels, the personal data including age, sex or the like is referred to,and, for a subject with high physical strength level, initial values ofthe exertion load level and of a load increasing rate are set high. Itshould be understood, however, in order to maintain high precision inestimation, the load increasing rate exceeding a certain level, e.g., 40W/min, is not applied in this case.

After the exertion load test, the physical strength and the AT level areestimated (ST39). Thereafter, a determination is made whether the ATestimation was possible (ST40). If the AT estimation was not possible, astatistical AT level, for example, 55% of the maximum heartbeat rate, isestimated from the estimated physical strength level (maximum heartbeatrate) (ST41), and output with the physical strength level (ST42). If itwas possible to estimate the AT in ST40, thus estimated AT level and thephysical strength level are likewise output (ST42).

The above-described tests of physical strength and AT are conducted asfollows. For the AT, the heartbeat rate interval data obtained by theexertion load test is used to find a relation between the heartbeat rateand the entropy of the fluctuation of heartbeat rate intervals as shownin FIG. 8. The AT is obtained as a heartbeat rate at the minimum pointof the entropy.

To obtain the entropy of the heartbeat rate fluctuation, the PI is firstcalculated using the RR data and the following expression (2).

PI(n)%={RR(n)−RR(n+1)}/R(n)×100  (2)

From 128 pieces of such PI data, or at an interval of every two minutes,frequency distribution in percentage is calculated. P(i)=fi/f is thenfound, and the entropy H is calculated using the expression (1)explained in conjunction with FIG. 4.

Next, the physical strength level corresponding to the maximum exertionintensity is estimated based on the estimated AT, by finding a slope ofthe heartbeat rate change with respect to the exertion load level (W)within a predetermined range of, e.g., ±20 beats around the heartbeatrate at the estimated AT level, as shown in FIG. 9. If the AT estimationwas not possible, a similar estimation is carried out in a range of ±20beats around an index that is determined by {(200−age)−heartbeat rate atrest}×0.55+heartbeat rate at rest.

Accordingly, it is possible to estimate, from the electrocardiographicsignal obtained at the exertion load test, the AT and the physicalstrength simultaneously and efficiently in a least possible time period.

Each example described above has used the electrocardiographic signalmeasured by the electrocardiographic sensor as a physiological signal,and has employed the fluctuation of heartbeat rate intervals forestimation. Instead of the electrocardiographic signal, DP (DoubleProduct) (blood pressure×heartbeat rate) or a breathing rate may be usedas the physiological signal. The blood pressure during exercise can bemeasured, for example, by contacting handle 12 of the bicycle ergometerwith a cuff 50 of a blood pressure gauge for finger, as shown in FIGS.14A, 14B. In FIG. 14B, 51 denotes an air tube with a pulse signal line52. The heartbeat rate can of course be measured by various kinds ofelectrocardiographic sensors as described above. The breathing rate ismeasured by attaching a thermistor 53 to the nose of the exercisingperson M. Thermistor 53, which is held, for example, by a tape 54widening the nostril (see FIG. 15B), detects the temperature change dueto breathing to measure the breathing rate.

In addition, although the bicycle ergometer has been used as the loaddevice capable of changing a load in each example described above, thepresent invention is also applicable to a treadmill as shown in FIG. 16,a rowing ergometer in FIG. 17, or the like.

Referring to FIG. 16, a running belt is denoted by 21. A manipulationunit 22 includes a display portion, a key input portion and the like.When a power supply switch 23 is turned on, a built-in motor starts tomove running belt 21. A person about to do exercise gets on this runningbelt 21, adjusts the moving rate of the belt, and starts running. Inthis treadmill, changing the number of rotation of the motor or theangle of inclination of the running belt can change the load.

The rowing ergometer shown in FIG. 17 includes a seat 31, a rail 32, apower supply switch 33, a foot rest 34, a bar 35 and a manipulationpanel 36. A person about to do exercise sits on seat 31 and pulls thebar 35 with a rope attached thereto close to him/her and returns it backto its initial position repeatedly, so that he/she can do exercisefeeling the load power incorporated. In this rowing ergometer, changingthe tensile force of the bar that works to let it return to its initialposition can alter the load.

(2) Second Embodiment

Hereinafter, the second embodiment of the present invention will bedescribed. In the second embodiment, the anaerobic threshold isestimated utilizing a power of the fluctuation of heartbeat rateintervals. A bicycle ergometer being used and data being obtained from atest subject in the second embodiment are similar to those in the firstembodiment.

FIG. 18 is a flow chart showing contents of electrocardiographic signalprocessing according to the second embodiment. Referring to FIG. 18, inthis embodiment, the electrocardiographic signal at rest is firstdetected (ST51). Calibration is then conducted, start of measurement isdisplayed, and load control is started (ST52-ST54). The steps heretoforeare the same as in the first embodiment.

In the second embodiment, the peak of the electrocardiographic signalfrom electrocardiographic sensor 1 is detected, and RR interval data(one cycle of the heartbeat rate) is calculated. Based on the RRinterval data, a power is calculated using the following expression (3):

power(n)[ms² ]={RR(n−1)−RR(n)}²  (3)

That is, the power is the square of the difference between the previousRR interval and the current RR interval. Herein, this power is called apower of the fluctuation of heartbeat rate intervals. The average valueof this power data for 30 seconds, detected in 15 seconds, is used forestimation of the anaerobic threshold as an example of the exertionlevel.

Next, in ST56, a determination is made whether the AT point has beenreached. FIGS. 19A and 19B illustrate changes of the power of thefluctuation and the load over time. As shown in FIGS. 19A and 19B, thepower of the fluctuation decreases to converge as the exertion loadincreases. The convergence point of the curved line showing thevariation in the power of the fluctuation corresponds to the AT point.Herein, the convergence point is determined so when the power of thefluctuation becomes lower than a predetermined bottom value and when thedifference from the previous power value (power (n−1)−power (n): slopeof the curved line showing the variation of the fluctuation power)becomes lower than a predetermined reference value.

The load is increased until the AT point is obtained (ST57). When theanaerobic threshold point is reached (YES in ST56), the result isdisplayed, the load is decreased, and the load control is terminated(ST58-ST60). These steps are again the same as those in the firstembodiment.

(3) Third Embodiment

Now, the third embodiment of the present invention will be described. Aload of exercise may be controlled employing an oxygen intake, which iscalculated from a load upon appearance of the anaerobic thresholddetected by a method of either the first or the second embodiment. Theoxygen intake (VO2) is calculated from the load at the time ofappearance of the AT using a conversion formula, and VO2 per 1 kilogramof weight is obtained.

For example, when a person weighing 70 kg exercises with a bicycleergometer and the AT appears at 100W, then the oxygen intake iscalculated by the following expression (4):

VO2(ml/kg/min)=load (W)÷0.232×14.3÷5.0+weight (kg)  (4)

Herein, 0.232 means that the exercise efficiency of the bicycleergometer is 23.2%. 14.3 is a conversion coefficient of 1 watt=14.3cal/min. 5.0 is a conversion coefficient meaning that 5.0 kcal isconsumed with the oxygen consumption of 1 litter. The operation resultis as follows:

VO2(ml/kg/min)=100÷0.232×14.3÷5.0÷7.0=17.6

This means that the VO2 at the time of appearance of the anaerobicthreshold is 17.6 (ml/kg/min).

As the AT of a healthy person generally appears at about 5.5% of themaximum oxygen intake (VO2max), the physical strength is measured byregarding the 55% of the standard value of VO2max at each age as thestandard value of the anaerobic threshold.

(4) Fourth Embodiment

Now, the fourth embodiment of the present invention will be described.In the fourth embodiment, the method of detecting the anaerobicthreshold as an example of the exertion level described in the firstthrough third embodiments is applied to a pulse rate meter such as aheartbeat rate meter.

The configuration of the heartbeat rate meter according to the presentembodiment is shown in FIG. 20. Referring to FIG. 20, the heartbeat ratemeter of this embodiment includes: a heartbeat rate sensor 61; apreamplifier 62 amplifying a heartbeat rate signal detected by heartbeatrate sensor 61; a filter 63 removing noise; an amplifier 64 furtheramplifying the heartbeat rate signal amplified and filtered; an A/Dconverter 65; a CPU 66 performing various kinds of processing includingestimation of an anaerobic threshold; a key input device 67; a display68; a memory 69; and an alarm 70.

With the heartbeat rate meter according to the present embodiment, whenthe heartbeat rate reaches the AT level, alarm 70 notifies that it is atthe anaerobic threshold level. Display 68 displays the same information.Display 68 and alarm 70 also designate a pace of exercise at theanaerobic threshold level. Further, an exercise time with exertionintensity within a target zone that is set on the basis of the anaerobicthreshold, and an exercise time with exertion intensity stronger orweaker than the exertion intensity in this range are calculated, andalso displayed on display 68. The respective exercise times are storedin memory 69.

FIG. 21 shows, by way of example, how the heartbeat rate meter accordingto the present embodiment is worn. This heartbeat rate meter is formedof an enclosure 71 and a body 72 in the form of a wristwatch. Enclosure71 includes electrocardiographic electrodes 73 and a transmitter 74, andbody 72 receives the heartbeat rate signal transmitted. In terms of thecircuit configuration, a transmitting unit and a receiving unit areprovided anywhere between preamplifier 62 and A/D converter 65 shown inFIG. 20. Although body 72 is shown in the form of wristwatch, it may bea box having a manipulation panel or the like, dependent on a type ofexercise.

Now, the processing operation of the heartbeat rate meter according tothe present embodiment will be described with reference to the flowchart shown in FIG. 22. When start key depress information is input fromkey input device 7 to CPU 6, the measurement is started, and adetermination is first made whether it is an AT input mode (ST71). Ifso, the AT pitch previously determined or the like is input, or read outfrom memory 69 (ST77). Thereafter, step ST76 and subsequent steps arecarried out, which will be described later.

In ST71, if it is not the AT input mode and if the AT should beestimated, then a rest state is designated by alarm 70, and theheartbeat rate data at rest is input to CPU 66. At this time,calibration is performed such that the signal from heartbeat rate sensor61 attains a prescribed fixed level (ST72).

Next, alarm 70 demands an exercise at a pitch corresponding to that ofwalking. The heartbeat rate data at this time is taken into CPU 6. Theanaerobic threshold is then estimated (ST73). For this estimation of theanaerobic threshold, the pitch is gradually increased, and thecorresponding heartbeat rate data are taken into CPU 66. The RR intervaldata is extracted, and then, the PI is calculated. Here, the PI iscalculated by the expression (2) described above.

From 128 pieces of the PI data, or at an interval of every two minutes,frequency distribution in percentage is calculated. From P(i)=f(i)/f,according to the expression 2 as in the first embodiment, the minimumpoint of the entropy is detected and the anaerobic threshold isestimated (ST73, ST74).

The heartbeat rate and the pitch at this time are stored as the ATheartbeat rate and the AT pitch in memory 69, while they are displayedon display 68 and notified by alarm 70 (ST75).

Next, the AT pitch is used to set a pace of exercise. This pace ofexercise is designated via display 68 and alarm 70 (ST76). Adetermination is then made whether the exercise is being done with theexertion intensity within a target zone that is set based on the ATpitch, or it is being done with the exertion intensity stronger orweaker than that in this range (ST78). According to the determination,“appropriate” (ST79), “strong” (ST80) or “weak” is displayed (ST81).Exercise times corresponding to respective exertion intensities arestored in memory 69 and displayed on display 68 (ST82). Alternatively,they may be only displayed on display 68 or only stored in memory 69.

In the heartbeat rate meter shown in FIG. 21, if a pulse rate sensor 61a is used in place of heartbeat rate sensor 61, it becomes a pulse ratemeter, which can be utilized in the same manner as the heartbeat ratemeter.

In the fourth embodiment, entropy is used for detection of the anaerobicthreshold. Not limited thereto, however, the anaerobic threshold mayalso be detected employing the second or third embodiment.

Further, in the embodiments above, the anaerobic threshold has been usedas the exertion level. Not limited thereto, however, the exertion levelmay of course be obtained employing any other data as long as it isbased on the change of a physiological signal corresponding to thechange of a load of the load device.

Industrial Applicability

As explained above, the exercise machine according to the presentinvention estimates the anaerobic threshold based on anelectrocardiographic signal corresponding to the change of a load of theload device, and controls the load based on the estimated value. Thus,an exercise machine permitting each person to do appropriate exercise inconformity with his/her own physical strength can be provided.

What is claimed is
 1. An exercise machine, comprising: a load devicecapable of changing a load; a physiological signal measuring unitmeasuring a physiological signal noninvasively over time; an exertionlevel estimating unit estimating an exertion level based on thephysiological signal corresponding to a change of the load of said loaddevice; and a changing unit changing the load of said load deviceemploying the estimated exertion level; said load device being capableof gradually increasing the load over time, said physiological signalmeasuring unit being an electrocardiographic sensor detecting anelectrocardiographic signal, said exertion level estimating unitestimating the exertion level based on the electrocardiographic signaldetected while said load is gradually increased, and said exertion levelestimating unit estimating, as said exertion level, an anaerobicthreshold based on a fluctuation of heartbeat rate intervals in eachelectrocardiographic signal detected.
 2. The exercise machine accordingto claim 1, wherein said exertion level estimating unit includes a unitfor calculating the fluctuation of heartbeat rate intervals in eachelectrocardiographic signal detected, a unit for calculating entropy ofthe fluctuation of heartbeat rate intervals, and a unit for finding aminimum point of a characteristic change of the entropy with respect toan increase of the load, and estimates a load corresponding to theminimum point as the anaerobic threshold.
 3. The exercise machineaccording to claim 1, wherein said exertion level estimating unitcomprises a unit for calculating the fluctuation of heartbeat rateintervals in each electrocardiographic signal detected, a unit forcalculating a power of the fluctuation of heartbeat rate intervals and aunit for finding a convergence point of a change of the power withrespect to an increase of the load, said exertion level estimating unitestimating an exertion load corresponding to said convergence point asthe exertion level.
 4. The exercise machine according to claim 1,further comprising a unit for determining an exercise program based onsaid exertion level and a unit for outputting the exercise programdetermined.
 5. The exercise machine according to claim 4, wherein apitch or load is altered so that the exercise proceeds according to saidexercise program.
 6. The exercise machine according to claim 1, whereinsaid exertion level measuring unit evaluates aerobic working capacity bycalculating a ratio of the estimated exertion level to a maximumheartbeat rate, and outputting the evaluated aerobic working capacityfor display.
 7. The exercise machine according to claim 4, whereinaerobic working capacity is evaluated from an estimated value of oxygenintake at the estimated exertion level.